This invention relates to an improved gas-metal-arc welding process by which a high rate of metal deposition is achieved. The process is of the type which involves continuously feeding a consumable electrode wire towards the weld deposit with a shielding gas flowing around the end of the electrode and the arc gap between the electrode and the weld deposit. The shielding gas comprises a mixture of major proportions of argon and helium and minor proportions of carbon dioxide and oxygen. The electrical arc ionizes the gas to produce a plasma field or cloud in the gap between the free end of the wire electrode and the weld deposit. The plasma field is stabilized relative to the arc gap and electrode axis. Thus, large drops or globules, which are melted from the free end of the electrode, are transferred by free flight across the arc gap to the weld deposit location or substrate surface.
My prior U.S. Pat. No. 4,463,243, issued July 31, 1984, for a "Welding System," describes the underlying process and the four-gas mixture. The process is additionally described in my U.S. Pat. No. 4,572,942, issued Feb. 25, 1986, for a "Gas-Metal-Arc Welding Process."
The process may utilize a welding gun, such as that disclosed in my U.S. Pat. No. 4,464,560, issued Aug. 7, 1984, for an "Arc Welding Gun With Gas Diffuser and External Cooling Conduit," to John G. Church and Emerson G. Malone. Also, a suitable welding gun and this type of process are disclosed in U.S. Pat. No. 4,529,863, issued July 16, 1985, for a "Gas-Metal Arc Welding Method," to Jean-Claude Lebel.
The prior process produces a relatively high rate of deposition of weld material to rapidly form a high-quality weld bead. The rate of metal deposition, the speed of formation of the bead and the quality of the bead all are substantially better than in earlier welding processes.
In order to properly perform the process and secure the desired results of high-speed deposition and high-quality weld beads, it was believed that, along with a relatively high current density, the voltage applied to the electrode had to be held within certain limited ranges. For example, it was believed that when the voltage exceeded certain limits, it would become counterproductive and adversely effect the metal deposition and the quality of the bead.
More recently, I have discovered that, unexpectedly, the rate of metal deposition can be very substantially increased, with good or better quality of the weld bead, by substantially increasing the applied voltage beyond previous limits and by increasing the length of the arc gap. Thus, the invention herein concerns an improvement to the process described in the above-identified prior patents, which substantially increases the speed of depositing weld metal.